Reduced thermal conductivity of constricted graphene nanoribbons for thermoelectric applications

Graphene nanoribbons (GNRs) hold promise as thermoelectric (TE) materials due to their advantageous electronic properties compared to conventional candidates. However, a key challenge to enhancing the TE performance of GNRs lies in reducing the thermal conductivity while maintaining the electronic transport properties. To address this challenge - this study proposes a GNR-based structure featuring nanoscale constrictions named graphene nano constrictions (GNCs). This work systematically analyzes the thermal transport properties of these GNCs and compares them to conventional GNRs. Non-Equilibrium Molecular Dynamics (NEMD) simulations were employed to evaluate the lattice thermal conductivity of the material, and a marked reduction of thermal conductivity exceeding 74 % was observed in the proposed structures. Furthermore, it is revealed that the thermal conductivity of these structures can be further tailored by manipulating their physical geometry, focusing on the length and the constriction dimensions. Additionally, superlattice counterparts of the GNCs composed of graphene and h-BN are explored in this study. Subsequently, an 88 % reduction of lattice thermal conductivity is observed in the superlattice counterparts of GNCs compared to GNRs. Overall, this study demonstrates the effectiveness of nanoscale constrictions in manipulating the thermal conductivity of GNR-based structures, creating a path for optimizing their TE performance and potential device applications.